Communication networks generally comprise nodes and linksets that connect the nodes to form the network. The basic elements of a conventional PSTN in a typical PSTN configuration are illustrated in FIG. 1. As seen in FIG. 1, the network includes signal transfer points (STPs), service switching points (SSPs), and service control points (SCPs). An STP is a network hub that provides routing of messages between other network nodes. An SSP may be a network end point to which subscriber terminals are connected, or may be a tandem point that handles trunk traffic for other SSPs. An SCP is a network endpoint that provides database services to subscribers such as calling number identification, voice mail, and toll-free calling.
The STPs, SSPs and SCPs and their associated link sets are collectively referred to as the signaling side of the communication network. The primary functions of the signaling side of the network are to establish connections between SSPs and to provide data management for network services. Once a connection is established between SSPs, voice or other data originated from subscriber terminals is carried by trunks such as the trunk 10 shown in FIG. 1.
It is typical in PSTNs to provide redundancy of STPs so that failure of an STP does not disable part of the network. STPs are typically deployed in mated pairs, such that each network node connected to an STP of a mated pair is also connected to the other STP of the mated pair. In the conventional PSTN illustrated in FIG. 1, it may be seen that each network node connected to STP A is also connected to STP A', and each network node connected to STP B is also connected to STP B'.
Communications among network nodes in the signalling side of the network may be routed using point codes. A point code corresponds to a physical device that constitutes a network node. Communications between two network nodes include an originating point code (OPC) that identifies the node originating the message, and a destination point code (DPC) that identifies the node to receive the message. The ability of a node to receive a message from another node therefore requires knowledge of the node's point code at other nodes of the network. In the alternative, some messages may be routed using global title queries. A global title query specifies a logical address as the destination of the query, and a global title translation is performed on the query at an STP to determine a physical address for use as the DPC of the message.
Under some circumstances it is necessary or desirable to change or augment the device that constitutes a network node. For example, an existing device may be replaced by a new device in order to provide enhanced capabilities at that node. Similarly, a new device may be added to supplement an existing device, for example, to enable a wider range of services or to expand the number of link sets to the node. The new device may provide supplemental functions, and/or may also duplicate functions of the original device.
In accordance with conventional practice, a node is replaced by disconnecting all links to the existing device and reestablishing those links to the new device, which then assumes the point code of that node. However, this can have the undesirable effect of disabling part of the network during the replacement process. Alternatively, in accordance with conventional practice, a device may be replaced or supplemented by the addition of a new device having a new point code. However, this practice can have the undesirable effect of requiring reconfiguration of the other network nodes to recognize the new point code of the new node. Other conventional methods for adding or augmenting node devices are cumbersome and may entail disadvantages similar to those noted above.